Overshot rotary bit

ABSTRACT

A rotary bit having a chamber and annular and sidewall cutting elements for cutting over an undersea wellhead and receiving said wellhead within the bit.

United States Patent [1113510350 [72] II1VCI'1101 g0. Seabgum I 5 Rehnnm CM vanger, orway [21 1 App]. 873,268 UNITED STATES PATENTS 22 Filed N 3 1969 583,317 5/1897 Wilson 175/403 p d Oct 5, 197 1,862,814 6/1932 Wright et al. 175/404 X I73] Assignee Phillips petroleum Commy 2,761,440 9/ 1956 Schwab 125/20 2,867,137 1/1959 Joy 175/411 X 2,902,261 9/1959 Standridge 175/403 X 54] OVERSHOT ROTARY BIT 3,456,747 7/ 1969 Elwell et al. 175/403 4 Claims 2 Drawing Primary Examiner-Ian A. Calvert [52] 11.8. CI 175/403, Attorney-Young and Quigg 175/41 1 [51} 1nt.Cl ElZb 2/16,

E21c 13/12 ABSTRACT: A rotary bit having a chamber and annular and Field of Search 175/327, sidewall cutting elements for cutting over an undersea wellhead and receiving said wellhead within the bit.

PATENTED UB1 5 [SH SHEET 1 [IF 2 32 FIG.

INVENTOR. E. O. SEABOURN BY zr -H A TTORNEYS PAIENTED 0m 5 Ian sum 2 or 2 FIG. 2

INVENTOR. E. O. SEABOURN BY 1. ff 1 Ms OVERSIIOT ROTARY BIT This invention relates to a bit for cutting material from around a wellhead. In another aspect, this invention relates to an overshot rotary bit for cutting over an undersea wellhead and receiving said wellhead within the bit.

In the completion of offshore wells, cement is utilized to fixedly and sealably attach casing to the walls of a well bore. Equipment utilized in cementing this casing sometimes malfunctions and permits cement to flow around the wellhead connections at the top of the casing located on the ocean floor. This condition is often not noticed until the cement sets up and attempts are made to enter the wellhead and casing for further drilling or well completion operations. In these cases it then becomes necessary to remove the cement encapsulating the wellhead connections in order to install equipment thereon. This cement removal generally requires a diver working upon the floor of the ocean which is expensive, maintains large quantities of drilling equipment idle, and, most important, endangers the lives of those required to work at the sometimes extreme water depths. Similar wellhead entrance problems also may arise from mud fiows and other material covering the wellhead and preventing access thereto.

It is therefore an object of this invention to provide an apparatus for removing material from around a wellhead. Another object of this invention is to provide an apparatus for cutting cement from around a wellhead positioned beneath the surface of the water. Other aspects, objects, and advantages of the present invention will become apparent from a study of the disclosure, the appended claims and the drawing.

In the drawing FIG. I is a diagrammatic frontal view of the bit of this invention and FIG. 2 is a bottom view of the bit.

In FIG. 1 the first end portion of the bit of this invention is designated generally by numeral 2. The first end portion 2 comprises a threaded portion 4 constructed to be attached to a string of drill pipe. The threaded portion 4 is preferably fixedly attached to downwardly and outwardly extending supporting members 6 but can be an integral part of said members 6. A separate elongated cutting element 8 or scraper is attached to each supporting member at equally spaced-apart arcuate distances relative to the longitudinal axis of the threaded portion 4 of the first end portion 2. These cutting elements 8 each extend substantially vertically downwardly from the first end portion 2 and are positioned to radiate outwardly therefrom. The cutting elements 8 preferably have a thickness in the range of Who l kinches with an outer edge surface 10 being a planar surface tangent to a circle circumscribed about the axis of the threaded portion 4 of the bit. The inner surface 12 of each cutting element 8 is preferably blunt to prevent damage to the wellhead and the outer surface 10 is preferably covered with a carbide layer 14 to provide a hard cutting surface that does not readily dull and chip during drilling operations. The lower end 16 of each cutting element 8 is preferably a planar surface substantially perpendicular to the axis of the threaded portion 4 and preferably is covered by a carbide layer 14 as described above to form a cutting surface thereon. In order to provide rugged construction and for the distribution of forces relatively equally spaced upon the bit, it is preferred that there be at least three supporting members and elongated cutting elements 8 on each bit.

A cutting ring 18 is rigidly attached on an upper surface 20 to each of the elongated cutting elements 8. As shown in FIG. 2, it is recommended that the ring 18 be mounted in a slot formed in the lower end 16 of each cutting element 8 in order to rigidly attach the ring 18 to the individual elements 8. A lower cutting surface 22, preferably covered by a carbide layer 14, is formed on the lower surface ofthe ring 18. It is important that the lower cutting surface 22 of the ring 18 be at the same or a lower elevation than the lower cutting end 16 of each cutting element 8. If the lower cutting surface 22 of the ring 18 is positioned at an elevation higher than the lower cutting ends 16 of the elements 8, it has been found that excessive stresses are imparted to the elements 8 and the cutting rate of the bit is reduced, To improve the cutting rate of the bit of this invention it is preferred that a plurality of notches 24 be formed on the lower cutting surface 22 of the ring 18 with each notch 24 having a first side 26 extending vertically and upwardly into the ring 18 and a second side 28 angled downwardly and outwardly toward the direction the bit is desired to be rotated. Since bits are generally rotated to the right, it is preferred that, as viewed from above, the second side 28 of each notch 24 extend in a clockwise direction from its respective first side 26.

The cutting ring 18, cutting elements 8, and first end portion 2 are constructed so that upon attachment one to the other a chamber 30 is formed upwardly through the bit with said chamber 30 open on the second end portion 32 of the bit for receiving a wellhead. The inside diameter of this chamber 30 is dependent upon the dimensions of the particular wellhead over which bit is constructed to be operated. It is important, however, that the inside diameter of the bit chamber 30 be in the range of not less than it-inch nor more than 1% inches greater than the diameter of the portion of the wellhead over which the bit is to be urged. If a chamber having a greater relative diameter is used, it has been found that efficient and complete removal of cement from the wellhead surface cannot be assured. If a chamber having a smaller relative diameter is utilized, then the outer surfaces of the wellhead are often damaged and drilling rates are reduced owing to binding of the bit upon the wellhead.

During the operation of the bit, the bit is lowered on drill pipe over the wellhead encapsulated by cement or covered with other material and thereafter is rotated at a slow rate of speed. Sometimes a portion of the wellhead will be above the surface of the encapsulating material and correct positioning of the bit can be made by viewing the position of the bit through an underwater TV camera. Where the wellhead is completely covered, the slowly rotating bit will chip off cement and upon striking metal will generally align itself relative to the axis of the wellhead owing to the small area of the bit in contact with the material relative to the large diameter of the bit. If the placement of the bit is considerably removed from the buried wellhead, the bit operates to fragment and break up the concrete for discovery of the portion of the wellhead and the subsequent cutting over thereof.

Other modifications and alteration of this invention will become apparent to those skilled in the art from the foregoing discussion and accompanying drawing, and it should be understood that this invention is not to be unduly limited thereto What is claimed is: 1. A bit for cutting and removing material encompassing a wellhead, comprising a body with a threaded first end portion for attachment of said bit to a string of drill pipe and a second end portion and means attached to the second end portion of the body and defining a chamber for receiving a wellhead into the chamber while rotating the bit by the drill pipe comprising. at least three elongated cutting elements attached at equally spaced-apart arcuate distances to the second end of the body, each of said elements extending downwardly, each element having an elongated blunt inner surface, an elongated outer cutting surface, and a lower cutting end; and

an annular cutting ring attached to the cutting end of the elongated cutting elements and substantially coaxial with said body and having a cutting surface formed on the lower surface thereof with said lower cutting surface of the ring being in a plane not higher in elevation than the lower cutting end of each elongated cutting element, said outer cutting surface of said elements lying outside the periphery of said annular ring.

2. A bit, as set forth in claim 1, wherein the cutting surfaces of the elongated cutting elements and the annular cutting ring are covered with a carbide layer.

3. A bit, as set forth In claim I, wherein a plurality of notches are formed on the cutting surface of said annular cutting ring with each notch having a first side extending vertically and upwardly into said ring and a second side angled downwardly toward the direction said bit is desired to be rotated.

4. A bit, as set forth in claim I, wherein the diameter of the chamber of the bit is in the range of three-fourths to 1% inches greater than the diameter of the portion of the wellhead over which said bit is constructed to operate. 

1. A bit for cutting and removing material encompassing a wellhead, comprising a body with a threaded first end portion for attachment of said bit to a string of drill pipe and a second end poRtion and means attached to the second end portion of the body and defining a chamber for receiving a wellhead into the chamber while rotating the bit by the drill pipe comprising: at least three elongated cutting elements attached at equally spaced-apart arcuate distances to the second end of the body, each of said elements extending downwardly, each element having an elongated blunt inner surface, an elongated outer cutting surface, and a lower cutting end; and an annular cutting ring attached to the cutting end of the elongated cutting elements and substantially coaxial with said body and having a cutting surface formed on the lower surface thereof with said lower cutting surface of the ring being in a plane not higher in elevation than the lower cutting end of each elongated cutting element, said outer cutting surface of said elements lying outside the periphery of said annular ring.
 2. A bit, as set forth in claim 1, wherein the cutting surfaces of the elongated cutting elements and the annular cutting ring are covered with a carbide layer.
 3. A bit, as set forth in claim 1, wherein a plurality of notches are formed on the cutting surface of said annular cutting ring with each notch having a first side extending vertically and upwardly into said ring and a second side angled downwardly toward the direction said bit is desired to be rotated.
 4. A bit, as set forth in claim 1, wherein the diameter of the chamber of the bit is in the range of three-fourths to 1 1/4 inches greater than the diameter of the portion of the wellhead over which said bit is constructed to operate. 